In this article the HPLC modelling software, DryLab, is used to model a separation of pharmaceutical analytes using gradient time, temperature and ternary composition. Probably the most common approach for computer modelling is using a combination of gradient time and temperature, so this approach adds the potential use of ternary mixtures of mobile phases and brings the increased selectivity options that this will provide. This article will be of interest to anyone using computer simulation as part of their method development strategy.